binfmt: replace deprecated strncpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

There is a _nearly_ identical implementation of fill_psinfo present in
binfmt_elf.c -- except that one uses get_task_comm over strncpy(). Let's
mirror that in binfmt_elf_fdpic.c

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://github.com/KSPP/linux/issues/90
Cc:  <linux-hardening@vger.kernel.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240321-strncpy-fs-binfmt_elf_fdpic-c-v2-1-0b6daec6cc56@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 1920ed69279b5805f21ba66772dd661b6e3042e8..3314249e867474ff81075b4e007030caaf0fcd2e 100644 (file)
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1359,7 +1359,7 @@ static int fill_psinfo(struct elf_prpsinfo *psinfo, struct task_struct *p,
        SET_UID(psinfo->pr_uid, from_kuid_munged(cred->user_ns, cred->uid));
        SET_GID(psinfo->pr_gid, from_kgid_munged(cred->user_ns, cred->gid));
        rcu_read_unlock();
-       strncpy(psinfo->pr_fname, p->comm, sizeof(psinfo->pr_fname));
+       get_task_comm(psinfo->pr_fname, p);
 
        return 0;
 }